1. Field of the Invention
The present invention relates to an ATM exchange apparatus and to an ATM exchange method in the ATM exchange apparatus.
2. Description of the Related Art
One communication system for accommodating a plurality of types of data such as video data, audio data, and information processing data in a predetermined packet and exchanging and transmitting them together is the asynchronous transfer mode (ATM) system. Use of this ATM system for the connection of an information network for transmitting multimedia information and the plurality of multimedia apparatuses in the general home via an inexpensive ATM system exchange (ATM exchange) introduced into each home and provision of sophisticated multimedia information services is being considered.
In the ATM system, the data is transmitted in units of 53 byte ATM cells. (as mention later by referring to FIG. 8) Internal processing such as exchange processing is frequently carried out in units of ATM calls as well. Here, in the ATM exchange, for example, when adding an identifier of the input port to an ATM cell so as to notify the routing processing unit of the ATM exchange of the input port receiving the ATM cell or when adding an identifier for the congestion control and priority control to the ATM cell so as to notify it of the ATM cell covered by this control, it sometimes becomes necessary to serially add control data between the ATM cells.
Also, when carrying out real time high speed exchange processing, for example an exchange of ATM cells accommodating video data, there are cases where the ATM exchange is required to continuously process the ATM cells.
However, there is a disadvantage that if control data is further serially added to a train of ATM cells, the data will become too long in length, so the processing will become difficult or excessive time will become necessary for the processing.
For example, as a method for compensating for the excessive processing time caused due to the addition of the control data to the train of the ATM cells, the method of raising the frequency of the clock of the ATM exchange or increasing the bus width can be considered, but when this method is adopted, there arise disadvantages that the process of production of the LSI used in the processing apparatus becomes difficult, the size of the LSI becomes large, etc.
Further, for example, in internal processing of an LSI, provision of a register for storing the control data enables the addition of the control data to the train of ATM cells to be avoided. Accordingly, in actuality, it becomes necessary to insert the control data into the ATM cells in only part of the processing of the ATM exchange such as the transfer of data between LSI's or storage of the ATM cells in the memory. That is, since the insertion of the control data into the train of ATM cells becomes necessary in part of the processing of the ATM exchange, this leads to a reduction of the processing capability of the ATM exchange as a whole.